Transmitters, receivers, and transceivers for broadcast devices, such as cellular phones, are designed using radio frequency (RF) and analog blocks that have several imperfections. Various functional design restrictions, as well as broadcasting requirements and best practices, require that the various components of the cellular transmitter, receiver, and/or transceiver meet difficult design specifications.
The issue of meeting these design specifications can be addressed through analog design methods. That is, either extra circuitry and/or extra design time are used in order to achieve the required performance. The extra circuitry and/or circuit methods used to address these issues can often lead to more power consumption in the final design. Additionally, the added circuitry and/or circuit design involves the designer spending extra design time applying complicated design techniques in order to reduce the variation in output. Often, this might involve temperature and frequency compensating circuits that add to the complexity and die area of the design.
The issues can also be addressed using factory calibration. Using this method, less time is spent on additional analog design and/or design time in exchange for doing compensation for the imperfections in mass production. In order to support this, digital compensation circuits are added that can compensate for the various analog imperfections. For example, simple digital circuits can be added to offset imperfect analog signals. The compensation circuits can be small and easy to design, thus representing an improvement over using more complicated analog-only circuit design. However, in order to support the various compensations, this method requires factory calibration, meaning that various test signals must be injected and measured during mass production of the circuitry in the factory to determine the offsets to be used in the compensation circuits. Therefore, the negative aspect of this method is increased factory calibration time, which increases the cost of the end product.
These and other shortcomings are addressed in the description below.